cmd/pluginpkg: support relative path (pingcap#10205)

cmd/pluginpkg/pluginpkg.go

@@ -99,8 +99,19 @@ func main() {
 	if pkgDir == "" || outDir == "" {
 		flag.Usage()
 	}
+	pkgDir, err := filepath.Abs(pkgDir)
+	if err != nil {
+		log.Printf("unable to resolve absolute representation of package path , %+v\n", err)
+		flag.Usage()
+	}
+	outDir, err := filepath.Abs(outDir)
+	if err != nil {
+		log.Printf("unable to resolve absolute representation of output path , %+v\n", err)
+		flag.Usage()
+	}
+
 	var manifest map[string]interface{}
-	_, err := toml.DecodeFile(filepath.Join(pkgDir, "manifest.toml"), &manifest)
+	_, err = toml.DecodeFile(filepath.Join(pkgDir, "manifest.toml"), &manifest)
 	if err != nil {
 		log.Printf("read pkg %s's manifest failure, %+v\n", pkgDir, err)
 		os.Exit(1)
@@ -150,6 +161,7 @@ func main() {
 		"-ldflags", pluginPath,
 		"-buildmode=plugin",
 		"-o", outputFile, pkgDir)
+	buildCmd.Dir = pkgDir
 	buildCmd.Stderr = os.Stderr
 	buildCmd.Stdout = os.Stdout
 	buildCmd.Env = append(os.Environ(), "GO111MODULE=on")